'Shaping the Universe III - to Infinity and Beyond' printed from http://nrich.maths.org/

Previous articles have looked at the shapes of the earth and the
solar system. This final installment looks at what is beyond the
tiny part of the universe we live in and what exciting shapes can
be found there. All this is fairly recent astronomy, because for
thousands of years nobody knew that there was anything beyond the
planets and the stars that we can see. The stars were thought to be
all fixed into a giant sphere, like a canvas that acts as a
backdrop for everything else. Few people dared to think about what
was beyond that sphere, except perhaps heaven and hell.

Nowadays we know that our sun is just one of many billions of other
stars that make up our galaxy - the Milky Way. Sometimes on a very
clear and dark night you can see the Milky Way as a faint band of
clustered stars across the sky. The reason we can see our own
galaxy from inside it is because of its shape. Like many other
galaxies in the universe, our galaxy is shaped like a spiral.
Because we are located in one of the spiral arms, we can see the
rest of the galaxy sideways on. It's a bit like being an ant, and
sitting on one of the spokes of a bicycle wheel. We can still see
the rest of the wheel, but it just looks like a big line across the
sky because it is flat in the direction that we're looking.

Left: the
Milky Way as seen from earth. Picture by Jerry Lodriguss.

Right: an illustration of what astronomers
think the Milky Way would look like viewed from a distance (image
by NASA). The arrow shows approximately where our solar system
would be.

Galaxies come in ellipses, various types of spiral and other
amazing shapes too. There are lots of amazing pictures of galaxies
taken using powerful telescopes. Check out some more
astrophotography at http://www.astropix.com

Left: an unusual 'ring' galaxy known as
Hoag's Object (image by NASA)

Right: another spiral galaxy, called NGC1300
(image by NASA and the ESA) .

Unlike the shape of the earth and the structure of the solar
system, there is no way that we could have known anything at all
about galaxies without being able to observe them directly. Some of
them can just about be seen with the naked eye or a simple
telescope, but most galaxies can only be seen with the biggest
telescopes on earth, or the Hubble space telescope which is in
orbit around the earth. Using the data from these telescopes,
astronomers and astrophysicists use some very clever mathematics to
work out how big they are and what makes them the shape they
are.